How can you repair the fuel injector?

You replace it.

The old mechanical injectors you can...The newer electrical ones, NO

You cant really, leave it to a professional

You can attempt to clean them if they're clogged but if they're shorted internally you have to replace. It's best just to replace them anyways.

Clean it with solvent, or replace it.

You can't. You have to replace faulty injectors. But be sure that's the problem before you waste your money/. Injectors last well. Often the lifetime of the car.

Try to clean it, it can be blocked.

you replace. you can't repair

Hi No it needs to be replaced as it has failed to function.